private static NetworkMessageDelegate MessageHandler <T>(Action <INetworkPlayer, T> handler)
{
void AdapterFunction(INetworkPlayer player, NetworkReader reader, int channelId)
{
// protect against DOS attacks if attackers try to send invalid
// data packets to crash the server/client. there are a thousand
// ways to cause an exception in data handling:
// - invalid headers
// - invalid message ids
// - invalid data causing exceptions
// - negative ReadBytesAndSize prefixes
// - invalid utf8 strings
// - etc.
//
// let's catch them all and then disconnect that connection to avoid
// further attacks.
var message = default(T);
try
{
message = reader.Read <T>();
}
finally
{
NetworkDiagnostics.OnReceive(message, channelId, reader.Length);
}
handler(player, message);
}
return(AdapterFunction);
}
/// <summary>
/// Calls <see cref="Reader{T}.Read"/> and measures number of bytes read
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="reader"></param>
/// <returns></returns>
internal static T ReadWithDiagnostics <T>(NetworkReader reader)
{
var message = default(T);
// record start position for NetworkDiagnostics because reader might contain multiple messages if using batching
int startPos = reader.BitPosition;
try
{
message = reader.Read <T>();
}
finally
{
int endPos = reader.BitPosition;
int byteLength = (endPos - startPos) / 8;
NetworkDiagnostics.OnReceive(message, byteLength);
}
return(message);
}
